JPH1153604A - Correction method for optical sensor output - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately inspect the features of an inspection object without requiring a dead time after supplying power to a device. SOLUTION: At the time of adjustment, a correction value for each measurement time of a time measuring means 8 after power supply a device until generation of the stabilized output of a detection means 1 is calculated by using a ratio computing means 5, with its output stored in a correction value storage means 6. Then, at the time of actual operation, a correction computing means 7 respectively multiplies the correction value for each measurement time read from the correction value storage means 6 with the output value of the inspection means 1 and corrects optical sensor output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting a temporal change of an output of an optical sensor for optically detecting a characteristic of an inspection object.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting the output of an optical sensor for optically detecting the characteristics of an object to be inspected. Especially, it is explained as a bill. Accordingly, as a device for inspecting bills with this optical sensor, a bill discriminating device used in an automatic depositing and dispensing machine, a vending machine, and the like will be described below. In automatic depositing and dispensing machines, vending machines, etc., judgment of denominations on bills inserted by customers,
Further, a process for determining the authenticity is performed. A bill validator is used for this purpose.

[0003] This bill discriminating apparatus uses an optical pattern such as a reflected light or a transmitted light, based on a pattern or a figure of an inserted bill.
Alternatively, the magnetic pattern of the magnetic ink used to print the banknotes is detected, and the similarity is determined by comparing with a preset reference value, and the external dimensions of the banknote are detected. The discrimination is performed in combination with the result. At this time, an LED (light emitting diode), a photodiode, a phototransistor, or the like is used to detect an optical pattern, and a magnetic head or the like is used to detect a magnetic pattern. .

FIG. 3 is a block diagram of a conventional bill discriminating apparatus. The apparatus shown in FIG. 3 comprises a detecting means 1, a storing means 2, a reference value storing means 9, a characteristic calculating means 10, a comparing means 11, and a discriminating means 12. Is done. The detecting means 1 shown in FIG. 3 detects an optical pattern such as reflected light or transmitted light from a pattern or a figure of an inserted bill by an optical sensor using an LED, a photodiode, or a phototransistor, or detects a magnetic sensor. To detect a magnetic pattern and output a detection signal. Further, the storage means 2 stores the detection means 1
Is a memory for temporarily storing the detection signal detected by the.

[0005] The characteristic calculating means 10 calculates the characteristic amount of the bill from the detection signal read from the storage means 2 and supplies it to the comparing means 11. The comparison means 11 has one input side connected to the feature calculation means 10 and the other input side connected to the reference value storage means 9, and the feature amount of the bill calculated by the feature calculation means 10 and the reference value storage means 9 is compared with the reference value stored. The discriminating means 12 is connected to the comparing means 11 on the input side, and discriminates the denomination of the bill and the front / back of the bill from the comparison result between the characteristic amount of the inserted bill and a preset reference value. The judgment result of the inserted bill by the judgment means 12 is output to a higher-level device (not shown).

[0006]

However, in the device having the above structure, the detecting means 1 uses an LED, a photodiode, or the like.
Since an optical sensor using a phototransistor or the like is used, the output characteristic of the optical sensor becomes as shown in FIG. In FIG. 4, the output of the optical sensor is for a while (for example, about several minutes) after the power of the apparatus is turned on.
Means that the output changes greatly with time, and after a certain time t ₁ elapses,
It is shown that the output is stabilized for the first time.

FIG. 5 is a diagram showing a temporal change in the output of the optical sensor at a certain position of a bill and upper and lower reference values thereof. In FIG. 5, the solid line indicates when the power of the apparatus is turned on (hereinafter referred to as P-ON).
Shows the detection results obtained by scanning after the time t ₁ has elapsed, the shapes and patterns of the particular locations of a bill by the detection means 1 from. The broken lines above and below the solid line indicate an upper limit reference value and a lower limit reference value with respect to the detected value of this specific portion, respectively. The alternate long and short dash line indicates the detection result of the same portion immediately after P-ON.

As is clear from FIG. 5, before the time t ₁ from the time of P-ON until the output of the optical sensor stabilizes and reaches a constant value, the detecting means 1 detects the figure or pattern of the bill at the same position. Then, the detected value exceeds the upper reference value when the output is stable. That is, during the period from the time of P-ON to t ₁ , the discrimination is not performed correctly despite the similar pattern. Therefore, during the period from the time of P-ON until the time t _{1 at} which the output of the optical sensor is stabilized, it is not possible to accurately discriminate the banknote, and it is necessary to wait for the insertion of the banknote until the output of the optical sensor is stabilized. was there.

[0009]

According to the present invention, there is provided a method for correcting an output of an optical sensor for correcting a change with time in an output of an optical sensor for optically detecting a characteristic of an inspection object.
At the time of adjustment, the optical sensor output value is sequentially stored for each unit time from when the power to the device is turned on until the stable value of the optical sensor output is obtained, and then the stable value of the optical sensor output is stored. Divide by the stored optical sensor output value for each unit time and store the quotient in advance as a correction value for each unit time, so that during actual operation, the stable value of the optical sensor The optical sensor output value for each unit time until it is obtained is multiplied by the correction value for each unit time stored in advance and obtained as the corrected optical sensor output. It was done. As a result, the characteristics of the inspection object can be inspected with high accuracy even during the period from when the power is turned on to the time when the stable value of the optical sensor output is obtained, and the time required for waiting as in the conventional case is required. Is gone.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 is a configuration diagram of a bill discriminating apparatus according to Embodiment 1 of the present invention. In FIG. 1, a detecting means 1, a storing means 2, a reference value storing means 9, a feature calculating means 10, a comparing means 11 and a determining means 12 are the same as those in FIG. Reference numeral 3 denotes a correction unit according to the first embodiment, which includes a switching unit 4, a ratio calculation unit 5, a correction value storage unit 6, a correction calculation unit 7, and a time measurement unit 8.

Now, it is assumed that the detecting means 1 in FIG. 1 is an optical sensor using an LED, a photodiode, a phototransistor or the like. The storage unit 2 is a memory that temporarily stores the detection signal detected by the detection unit 1. The switching means 4 in the correcting means 3 is a means for performing switching control between a mode for calculating a correction value and a normal bill recognition mode. That is, switching means 4
Performs control to supply the output of the storage means 2 to the ratio calculation means 5 in the correction value calculation mode and to write the output of the ratio calculation means 5 to the correction value storage means 5, and to store the output in the normal operation mode. The output of the means 2 is supplied to the correction calculation means 7, and a control is performed to read a correction value corresponding to the time measured by the time measurement means 8 from the correction value storage means 6 and supply the correction value to the correction calculation means 7.

The time measuring means 8 measures the time for each unit time (for example, one second) from when the power is turned on to the apparatus, supplies the measured time to the correction value storage means 6, and sets the mode switching time t. ₁ is notified to the switching means 4. In the correction value calculation mode, the ratio calculation means 5 calculates a correction value from the time of P-ON to t _1, and stores the value by the correction value storage means 6. The correction calculation unit 7 reads the correction value from the correction value storage unit 6 and performs correction on the detection signal stored in the storage unit 2.

The comparing means 11 has one input side connected to the characteristic calculating means 10 and the other input side connected to the reference storing means 9. The reference value stored in the means 9 is compared. The discriminating means 12 is connected to the comparing means 11 on the input side, and discriminates the denomination of the bill and the front / back of the bill from the comparison result between the characteristic amount of the inserted bill and a preset reference value. The judgment result of the inserted bill by the judgment means 12 is output to a higher-level device (not shown).

The operation of the correcting means 3 in the apparatus having the configuration shown in FIG. 1 will be described in detail. (1) First, the operation in the correction value calculation mode will be described. The correction value P _tx from the time of P-ON to the time t _{1 at} which the output of the optical sensor stabilizes is obtained in advance in a process such as a test in a manufacturing process of the device. To this end, the output value of the optical sensor from the detecting means 1 is sequentially changed every unit time Δt (for example, the one second or the like) at which the time measuring means 8 performs time measurement using a reference medium (such as blank paper) determined at the time of design. Storage means 2
To be stored temporarily. That is, the attenuation curve until the output of the optical sensor in FIG. 4 is stabilized is plotted for each Δt on the time axis, and all output values indicated by black circles in the figure are temporarily stored in the storage unit 2.

Next, the ratio calculating means 5 sequentially calculates all correction values (correction coefficients) for converting all the temporarily stored output values indicated by black circles into output values at the time t ₁ . Outputs O _tx detecting means 1 at time t _x now from the time of P-ON, and the output of the time of the last time t ₁ and O _t1, the correction value P _tx at time t _x is the next ( It is obtained from the expression 1). P _tx = O _t1 / O _tx (1)

The numerical value of the correction value is gradually increased with time, for example, from about 0.5 immediately after the P-ON due to the inverse characteristic of the attenuation curve of FIG. Things. The calculation result is sequentially stored in the correction value storage unit 6 as a correction value for each unit time at which the time measurement unit 8 performs time measurement. When the storage of all the correction values in the correction value storage means 6 is completed, the correction value calculation mode ends.

(2) Next, a description will be given of a normal operation mode for discriminating bills. The arrival of the inserted bill is output from a bill detecting means (not shown) or a host device (not shown).
, The detecting means 1 enters an operating state. The detecting means 1 detects the pattern of transmitted light or reflected light which changes according to the density of a pattern or a figure of a bill by an optical sensor using an LED, a photodiode, a phototransistor, or the like, and the storage means 2 detects the pattern of one bill or Store for multiple sheets.

The correction means 3 performs the following corrections from the time of P-ON of the apparatus until the time measured by the time measuring means 8 reaches t ₁ , and does not perform the correction after t ₁ . That is, during the period from the time of P-ON until t ₁ when the output of the optical sensor is stabilized, the correction calculation means 7 reads the correction value from the correction value storage means 7 switched to read only by the time measurement means 8 from the time of P-ON. Time t
_The correction value P _tx is read in accordance with _x, and the output _Otx of the detection means 1 read from the storage means 2 is corrected using the following equation (2) to obtain a correction result O ′ _tx . O ′ _tx = O _tx × P _tx (2)

The correcting means 3, the measurement time t ₁ later by time measuring means 8 does not perform correction by the correction calculation unit 7. Next, the characteristic amount of the bill is calculated by the characteristic calculating means 10. Then, the comparing means 11 compares the reference value read from the reference value storage means 9 with the feature amount of the bill calculated by the feature calculating means 10 to determine the denomination of the bill and the front / back sides thereof. The judgment result of the inserted bill is output to a host device (not shown). The above operation is the same as in the case of FIG.

As described above, according to the first embodiment, the correction values corresponding to the output values of the individual optical sensors from when the power to the apparatus is turned on until the optical sensor outputs are stabilized are calculated and stored in advance. By doing so, even before the temporal change of the optical sensor output after the power supply of the apparatus is stabilized, the optical sensor output is corrected using the stored correction value, and the bill can be accurately discriminated. As a result, it is no longer necessary to wait for the insertion of banknotes as in the past.

Embodiment 2 FIG. 2 is a configuration diagram of a bill discriminating apparatus according to Embodiment 2 of the present invention. 2, the detecting means 1, the storing means 2, the reference value storing means 9, the feature calculating means 10, the comparing means 11, and the determining means 12 are the same as those in FIG. Reference numeral 3A denotes a correction unit according to the second embodiment, which includes a switching unit 4, a ratio calculation unit 5, an approximate expression calculation unit 6A, a correction calculation unit 7, and a time measurement unit 8. The correction means 3A in FIG. 2 is obtained by replacing the correction value storage means 6 in the correction means 3 in FIG. 1 with an approximate expression calculating means 6A, and the other means 4, 5, 7, and 8
Are the same as in FIG.

Therefore, in FIG. 2, the approximation formula calculating means 6A is provided in place of the correction value storage means 6 of FIG. 1, so that the approximation formula calculating means 6A and the means related thereto will be mainly described. I do. In FIG. 1, the correction value for correcting the attenuation curve of the optical sensor output of FIG. 4 is stored in the correction value storage unit 6 as individual correction data for each unit time for which the time measurement unit 8 performs time measurement. I have to. However, in apparatus using multiple light sensors and stores all the correction data for the individual light sensors to a unit time (e.g. 1 second) time t ₁ for each, it is a large-capacity memory is required as a whole unit.

Therefore, in FIG. 2, for each optical sensor, in the correction value calculation mode, the ratio calculation means 5 sets the P-
After calculating the individual correction data for each unit time from the time of ON to t ₁ , the approximation formula calculating means 6A calculates the approximate expression that approximates the individual correction data as a function of the elapsed time from the time of P-ON. Is calculated by using a method such as the least square method so that the approximation error is minimized.
Then, the calculated approximate expression is stored internally. As a result, a calculation time for calculating a correction value for each unit time from this approximate expression is required, but the memory capacity of the entire apparatus can be significantly reduced as compared with the case of FIG.

The operation of the apparatus having the configuration shown in FIG. 2 will be described mainly with respect to operations different from those in FIG. 1, and the other operations will not be described because they are redundant. (1) The operation in the correction value calculation mode will be described. P
Correction approximate equation until the time t ₁ of the optical sensor output stabilizes from the time -ON is obtained in advance in stroke such testing in a manufacturing process of the device. To this end, the output value of the optical sensor from the detecting means 1 is sequentially changed every unit time Δt (for example, the one second or the like) at which the time measuring means 8 performs time measurement using a reference medium (such as blank paper) determined at the time of design. It is temporarily stored in the storage means 2. That is, the attenuation curve until the output of the optical sensor in FIG. 4 is stabilized is plotted for each Δt on the time axis, and all output values indicated by black circles in the figure are temporarily stored in the storage unit 2.

Next, the ratio calculating means 5 sequentially calculates all correction values for converting all the temporarily stored output values indicated by black circles into the output values at the time t ₁ by the above equation (1). .

Next, the approximation formula calculating means 6A calculates the P
-An approximation formula that approximates all correction values per unit time from the ON time to t ₁ as a function of the elapsed time from the P-ON time so that the approximation error is minimized.
For example, it is calculated using a method such as the least square method. Then, the calculated approximate expression is stored internally. When the storage of the approximate expression in the approximate expression calculating means 6A is completed, the correction value calculation mode ends.

(2) Next, a description will be given of a normal operation mode for discriminating bills. The arrival of the inserted bill is output from a bill detecting means (not shown) or a host device (not shown).
The operations of the detecting means 1, the storage means 2, and the switching means 4 which enter the operating state upon being notified by a signal from are the same as those in FIG. Then, during the period from the time of the P-ON until the output of the optical sensor is stabilized until t ₁ , the correction calculating means 7 reads the approximate expression from the approximate expression calculating means 6 A switched to read-only, and measures the time by the time measuring means 8. The time is substituted into this approximation formula, a correction value for each measurement time is calculated, and the output _Otx of the detection means 1 read from the storage means 2 is corrected using the equation (2). O ′ _xt of

The correction means 3A, the measurement time t ₁ later by time measuring means 8 does not perform correction by the correction calculation unit 7. The operations of the reference value storage unit 9, the characteristic calculation unit 10, the comparison unit 11, and the determination unit 12 after the correction unit 3A are shown in FIG.
Is the same as

As described above, according to the second embodiment, similar to the first embodiment, even if the temporal change of the optical sensor output after the power supply of the apparatus is stabilized, the previously stored approximate By using the formula, the output of the optical sensor can be corrected to accurately discriminate bills, so that it is not necessary to wait for the insertion of bills as in the related art, and the memory capacity of the entire apparatus is reduced from that of the first embodiment. Can also be reduced. As an example, a time t ₁ until the output of each optical sensor is stabilized now.
Is 5 minutes and the counting unit time of the time counting means 8 is 1 second, it is necessary to store 60 × 5 = 300 correction values for each optical sensor. When this is stored as an approximate expression, although it depends on the approximation accuracy of the approximate expression, the above storage capacity of 1 to
Since about 20% is sufficient, the memory capacity of the entire apparatus can be significantly reduced as compared with the first embodiment.

In the first and second embodiments, the object whose characteristics are inspected by the optical sensor has been described as a bill, but the inspection object of the present invention is not limited to a bill. For example, checks, bills, passports,
The present invention can also be applied to an optical sensor that optically inspects these patterns (including a watermark pattern or the like), figures, dimensions, thicknesses, and the like using a specific paper sheet or the like as an inspection target.

[0031]

As described above, according to the present invention, in a method for correcting a temporal change of an output of an optical sensor for optically detecting a characteristic of an inspection object, the method comprises: The optical sensor output value is sequentially stored for each unit time until a stable value of the sensor output is obtained,
Next, the stable value of the optical sensor output is divided by the stored optical sensor output value for each unit time and the quotient is stored in advance as a correction value for each unit time. The optical sensor output value for each unit time from when the power is turned on until the stable value of the optical sensor output is obtained is multiplied by the previously stored correction value for each unit time, and the product is multiplied. Is obtained as the corrected optical sensor output, so that the characteristics of the inspection object can be inspected with high accuracy even when power is supplied to the apparatus until a stable value of the optical sensor output is obtained. This eliminates the need for conventional waiting times.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a bill validator according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a bill discriminating apparatus according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a conventional bill validator.

FIG. 4 is a diagram showing optical sensor output characteristics corresponding to a lapse of time after power-on.

FIG. 5 is a diagram showing a temporal change of an optical sensor output at a certain position of a bill and upper and lower reference values thereof.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Detection means 2 Storage means 3, 3A correction means 4 Switching means 5 Ratio calculation means 6 Correction value storage means 6A Approximate expression calculation means 7 Correction calculation means 8 Time measurement means 9 Reference value storage means 10 Feature calculation means 11 Comparison means 12 Discrimination means

Claims (4)

[Claims] 1. A method for correcting a temporal change of an output of an optical sensor for optically detecting a characteristic of an object to be inspected, comprising the steps of: starting from a time when power is supplied to an apparatus until a stable value of the output of the optical sensor is obtained; The output value of the optical sensor is sequentially stored for each unit time, and then the stable value of the output of the optical sensor is divided by the stored output value of the optical sensor for each unit time, and the quotient is divided for each unit time. Is stored in advance as the correction value of the optical sensor, and in actual operation, the optical sensor output value is stored in advance for each unit time from when the power is supplied to the apparatus until a stable value of the optical sensor output is obtained. A method for multiplying the correction value for each unit time, and obtaining the product as a corrected optical sensor output. 2. A method for correcting a temporal change of an output of an optical sensor for optically detecting a characteristic of an inspection object, the method comprising the steps of: during adjustment, from when power is supplied to the apparatus until a stable value of the optical sensor output is obtained. The output value of the optical sensor is sequentially stored for each unit time, and then the stable value of the output of the optical sensor is divided by the stored output value of the optical sensor for each unit time, and the quotient is divided for each unit time. The approximate value obtained by approximating the approximate value of the correction value for each unit time as a function of the elapsed time from when the power to the device is turned on is stored in advance, and the approximate value is stored in advance during actual operation. Read the approximate expression stored in advance,
Substituting the elapsed time for each unit time from the time of powering on the device to the approximation formula to obtain a correction value for each unit time, from the time of powering on the device until a stable value of the optical sensor output is obtained An optical sensor output value obtained by multiplying the obtained optical sensor output value for each unit time by the obtained correction value for each unit time to obtain a product as a corrected optical sensor output. Output correction method. 3. An optical sensor output for optically detecting a characteristic of an inspection object is an optical sensor output for optically detecting a pattern or figure of a paper sheet. The correction method of the optical sensor output described in the above. 4. An optical sensor output for optically detecting a characteristic of the inspection object is an optical sensor output for optically detecting a pattern or a figure of a bill.
Or the correction method of the optical sensor output according to 2.